My guess is it involved the nulled install of vBulletin and the keygenerator. No evidence to prove that's what caused the resource usage, but vB's known to be intensive during install, and I'm sure that keygen isn't helping things.
Granted, the bigger issue -now- is the suspension for warez, but it's more of a note for anyone else installing legitimate copies of vB - it will likely trip HRU. It did on the old system, it still does on the new one.